The invention relates to a hob having at least one heating zone having several elements and a method for operating such a hob.
FR 2 863 039 A1 discloses an induction hob having a plurality of inductors, which are arranged in a grid. A control unit detects cookware elements, which are placed on the induction hob and defines a heating zone having several heating elements for each cookware element. The shape, size and position of the heating zone are adjusted to the shape, size and position of the cookware element. The user can set a heating capacity of each of the heating zones by way of a user interface and the control unit operates the heating elements such that the desired heating capacity is distributed among the heating elements and/or inductors according to a predetermined heating capacity distribution.
To this end, the control unit determines a degree of cover for each inductor of the heating zones. The degree of cover corresponds to a proportion of the inductor, which is covered by a base of the detected cookware element. The heating capacity distribution then takes place essentially proportionately to the degrees of cover, so that inductors at the edge of the heating zone, which are only covered incompletely, are provided with a lower heating capacity than completely covered inductors. As a result, radiation losses at the edge of the heating zone are reduced.
The method known from FR 2 863 039 is very complicated in practice. On account of the reduced heating capacity of the inductors at the edge of the heating zone, the method also results in an inhomogeneous surface heating capacity. Operation of the inductors at the edge of the heating zone with a reduced heating capacity also results in proportionately higher switching and conduction losses in the inverters of the induction hob, which generate a high-frequency heating current for operating the inductors.
In large heating zones with numerous heating elements, an available heating capacity, which is generally limited by the available capacity in the domestic power network, is distributed among all heating elements in the case of large heating capacities. If the number of heating elements exceeds a critical value, all heating elements can therefore be operated with only a fraction of their maximum capacity. The switching losses and ohmic losses however increase with the number of heating elements, so that the efficiency is reduced overall.